linux-kernel - Re: [PATCH 03/12] Input: synaptics - fix minimum reported ABS_TOOL

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Date:	Fri, 8 Jul 2011 23:24:09 -0700
From:	Jeffrey Brown <jeffbrown@...roid.com>
To:	djkurtz@...omium.org
Cc:	dmitry.torokhov@...il.com, rydberg@...omail.se,
	chase.douglas@...onical.com, rubini@...l.unipv.it,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	derek.foreman@...labora.co.uk, daniel.stone@...labora.co.uk,
	olofj@...omium.org
Subject: Re: [PATCH 03/12] Input: synaptics - fix minimum reported ABS_TOOL_WIDTH

On Tue, Jun 28, 2011 at 10:07 PM,  <djkurtz@...omium.org> wrote:
> From: Daniel Kurtz <djkurtz@...omium.org>
>
> Synaptics touchpads report a 'w' value in each data report.
> For touchpads that support palm detection, when there is a single finger
> on the pad, the 'w' value reports its width in the range 4 to 15.
> Thus, the minimum valid width is 4.
>
> Note: Other values of 'w' are used to report special conditions:
>  w=0: 2 fingers are on the pad
>  w=1: 3 or more fingers are on the pad
>  w=2: the packet contains "Advanced Gesture Mode" data.

Ideally we should scale this to a physically meaningful quantity
instead, such as surface units.  That would require knowing the
distance between each capacitive touch channel and then scaling W - 4
by that amount before reporting it.

These values are all kind of mysterious to user-space anyways unless
the physical nature of the device is known by other means (such as
configuration files).

Jeff.
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